What I’ve learnt about different types of Covid vaccine

Hannah Do
4 min readApr 15, 2021


Disclaimer: This is my preliminary understanding derived from various sources I’ve read. This is subject to change as I learn more and as new data arrive, everything written below is NOT medical advice. I am not sponsored or linked to any vaccine producer.

All vaccines in the pipeline (Source: https://covid19.trackvaccines.org/)

A summary of what I’ve learnt about the current landscape of vaccines

There are eight main types of vaccines right now, I will be talking about what I’ve learnt about the four top types which have gained approval in at least one country. Each type will include: type name, what it means, example of producers or brand names of this type, known pros and cons and estimated range of their efficacies to date.

Eight types of Covid Vaccines (Source: https://covid19.trackvaccines.org/)

1. Inactivated Covid virus (China: Sinovac, SinoPharm, India: Bharat Biotech, and others)
Pros: a very well established vaccine type using inactivated virus to stimulate the immune response
Cons: potentially expensive to produce and low efficacy (around 50%-70%)

2. Non-replicating Vector vaccines: (UK-Sweden: Astra Zeneca, US: Johnsons and Johnsons, Russia: Sputnik, India: Covishield and others) used weakened or harmless modified cold viruses as vectors to deliver the spikes of the real virus.
Pros: newer way of delivering vaccine, can be very effective at low cost. Sputnik seemed to have delivered the best efficacy so far using two different modified cold viruses as vectors in two separate doses.
Cons: If the cold virus vector is well known to the body, it might get killed too quickly for the vaccine to be effective. If the vector is completely new to human (chimpanzee adenovirus in AstraZeneca), it’s hard to know how safe this is or if there will be rare side effects. Efficacy roughly from 60%-90% depending on the study/brand.

3. mRNA vaccines (US-Germany: Pfizer BioNTech, US: Moderna and others): Potentially the most modern type of vaccine out there using a messenger piece of RNA to instruct the body to create the Covid spike protein, the body then eliminate these spikes and learn how to protect itself against Covid.
Pros: high efficacy +90%, no life threatening side effect found so far.
Cons: potentially expensive, difficult to manufacture and distribute due to super low transportation temperature requirements.

4. Protein subunit (China: Anhui Zhifei Longcom, Russian: EpiVacCorona, US: Novavax, Vietnam: Nanocovax and others): Potentially the top choice of developing countries at the moment, this uses a fragment of a protein from the virus to stimulate our immune system.
Pros: potentially cheap, easy to manufacture and distribute, potentially high efficacy around 80%-90%.
Cons: adjuvants are normally needed to stimulate stronger immune responses.

A thought about advancing healthcare through Global collaboration

AstraZeneca and Pfizer/BioNTech Covid Vaccine Trials

Looking at this website , I see that Vaccine study trials take massive effort: Pfizer, AstraZeneca vaccines have been going through many trials in dozens of countries on many many thousands of people. I can’t even begin to imagine how much effort that must have taken.

On the flip side, a Vietnamese vaccine like Nanocovax struggled to recruit 600 people for phase 2 studies. I am not sure when phase 3 would happen. This seemed to be a problem across the board for developing countries developing protein subunit Covid vaccines.

2 Vaccines in Clinical Trials in Vietnam (A Taiwanese and a Vietnamese vaccine)

As a Vietnamese, I wonder why Vietnam choose to get into the route of protein subunit, not vector, not mRNA, not inactivated virus and found this very interesting. I realised that I would have chosen the same route for Vietnam considering the current landscape of efficacy, risk and feasibility. The one thing I might have done differently is this:

Problem hypothesis: For some countries like Vietnam, Taiwan, Cuba who are pursuing “protein subunit” as their go-to Covid vaccine, there has been a lot of difficulties in recruiting people for clinical trials (Taiwan, Vietnam), or recruiting people from more than one country (Cuba).

Solution hypotheses: For developing countries who are trying to develop similar types of vaccine, it is potentially much better to collaborate with similar stage countries to recruit and research for one product type. This should in theory decrease the investment cost per country and increase the chance of having enough trial recruits.

When looking further than just Vietnam, I realised that even for developed countries, the biggest breakthroughs have been by working together, not apart:
- Pfizer/BioNTech (Pfizer - an American company and BioNTech - a German company)
- Astra/Zeneca (Astra - a UK company and Zeneca - a Swedish company).

If the human species get to do this all over again, things might look very different. The below is my first effort to imagine how human might have structured it knowing what we know now:

- One platform for science community working on vaccine all over the world, everything is shared within limit
- Sub groups of countries and organisations who might want to pursue similar types of vaccines (mRNA, vector, subunit, inactivated)
- Opportunity for countries looking to build similar vaccines to collaborate funding, study effort and prepare for production ramp up together
- Opportunity for every countries and organisation to share data of side effects, observations, treatments and ideas

What would you have done differently if you’ve had the opportunity to influence the vaccine research and production set-up?



Hannah Do

A curious kid who is learning every day